Isotopes are variants of a particular chemical element which differ in neutron number, in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom; the term isotope is formed from the Greek roots isos and topos, meaning "the same place". It was coined by a Scottish doctor and writer Margaret Todd in 1913 in a suggestion to chemist Frederick Soddy; the number of protons within the atom's nucleus is called atomic number and is equal to the number of electrons in the neutral atom. Each atomic number identifies a specific element, but not the isotope; the number of nucleons in the nucleus is the atom's mass number, each isotope of a given element has a different mass number. For example, carbon-12, carbon-13, carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, 14, respectively; the atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7, 8 respectively.

A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example carbon-13 with 6 protons and 7 neutrons. The nuclide concept emphasizes nuclear properties over chemical properties, whereas the isotope concept emphasizes chemical over nuclear; the neutron number has large effects on nuclear properties, but its effect on chemical properties is negligible for most elements. In the case of the lightest elements where the ratio of neutron number to atomic number varies the most between isotopes it has only a small effect, although it does matter in some circumstances; the term isotopes is intended to imply comparison, for example: the nuclides 126C, 136C, 146C are isotopes, but 4018Ar, 4019K, 4020Ca are isobars. However, because isotope is the older term, it is better known than nuclide, is still sometimes used in contexts where nuclide might be more appropriate, such as nuclear technology and nuclear medicine. An isotope and/or nuclide is specified by the name of the particular element followed by a hyphen and the mass number.

When a chemical symbol is used, e.g. "C" for carbon, standard notation is to indicate the mass number with a superscript at the upper left of the chemical symbol and to indicate the atomic number with a subscript at the lower left. Because the atomic number is given by the element symbol, it is common to state only the mass number in the superscript and leave out the atomic number subscript; the letter m is sometimes appended after the mass number to indicate a nuclear isomer, a metastable or energetically-excited nuclear state, for example 180m73Ta. The common pronunciation of the AZE notation is different from how it is written: 42He is pronounced as helium-four instead of four-two-helium, 23592U as uranium two-thirty-five or uranium-two-three-five instead of 235-92-uranium; some isotopes/nuclides are radioactive, are therefore referred to as radioisotopes or radionuclides, whereas others have never been observed to decay radioactively and are referred to as stable isotopes or stable nuclides.

For example, 14C is a radioactive form of carbon, whereas 12C and 13C are stable isotopes. There are about 339 occurring nuclides on Earth, of which 286 are primordial nuclides, meaning that they have existed since the Solar System's formation. Primordial nuclides include 34 nuclides with long half-lives and 252 that are formally considered as "stable nuclides", because they have not been observed to decay. In most cases, for obvious reasons, if an element has stable isotopes, those isotopes predominate in the elemental abundance found on Earth and in the Solar System. However, in the cases of three elements the most abundant isotope found in nature is one long-lived radioisotope of the element, despite these elements having one or more stable isotopes. Theory predicts that many "stable" isotopes/nuclides are radioactive, with long half-lives; some stable nuclides are in theory energetically susceptible to other known forms of decay, such as alpha decay or double beta decay, but no decay products have yet been observed, so these isotopes are said to be "observationally stable".

The predicted half-lives for these nuclides greatly exceed the estimated age of the universe, in fact there are 31 known radionuclides with half-lives longer than the age of the universe. Adding in the radioactive nuclides that have been created artificially, there are 3,339 known nuclides; these include 905 nuclides that are either stable or have half-lives

Tim Greenwood

Truman A. Greenwood, known as Tim Greenwood, is a Republican politician who served in the Ohio General Assembly; as an attorney and political novice, Greenwood challenged incumbent Representative Arlene Singer in 1988. With the district being traditionally Republican, Greenwood won against Singer, he was sworn in on January 3, 1989. Greenwood won a second term with 58 % of the vote, he went on to win both the primary and general elections. He again was reelected for a fourth consecutive term. In 1994, Senator Betty Montgomery was elected as Ohio Attorney General, went on to resign from her Senate seat; as a result, a vacancy occurred, Greenwood was appointed to take her place. He resigned from the House in January 1995, was appointed in the Ohio Senate subsequently. However, only six months into his Senate tenure, Greenwood announced he would resign, citing an inability to spend time with his family, he resigned from the Senate in October 1995. Following his resignation, he returned to private law practice.

From 1999 to 2003, he served by gubernatorial appointment as a member of the Ohio Turnpike Commission. He serves as outside counsel for the Ohio Attorney General and is the Law Director of Sylvania Township

Robert Forrest Burgess

Robert Forrest Burgess is an American author of non-fiction adventure books, as well as sport fishing and scuba diving magazine articles. His photographs illustrate his material. Robert F. Burgess was born in Grand Rapids, Michigan, on November 30, 1927, he built his first diving gear out of a World War II gas mask, 50 feet of air hose, an air compressor to explore a Michigan shipwreck in 1944. At the end of World War II, he served as a ski trooper with the 88th Infantry Division named the Blue Devils by the Germans, took his GI Bill abroad, studying French first at the Berlitz Language School in Trieste, at the University of Neuchâtel in Switzerland. During this time he skied the Alps as part of the University's athletic program. Returning to Trieste to sell his German Amphibious Jeep, he and a companion purchased an Italian Lambretta motor scooter and rode it back to Switzerland, crossing the Great St. Gothard Pass and two other major mountain ranges at night. For their summer vacation he and a companion moved to Italy's Island of Capri for three months where they learned to skin dive.

After studying abroad he returned to the U. S. to complete his education. Moving to Florida he wrote and photographed features for every major U. S. outdoor magazine including several abroad. With his new bride, Burgess returned to Switzerland in 1956. In Milan they purchased an Italian Lambretta motor scooter that winter, riding it 700 miles, across the Rivieras to Spain, where they took a ferry to the Balearic Islands, they wintered on the island of Majorca, where he fished with Majorcan trawler fishermen, gathering material for a novel. That spring they ferried to Valencia and motor scootered across Spain to Madrid, where he and his wife lived for the next 3​1⁄2 years. While there Burgess wrote his first novel and numerous travel articles for periodicals in England and America. During that time, on assignment for "Argosy" Magazine, he and a companion crossed the Mediterranean aboard a freighter with the French Foreign Legion back-packed through Tunisia to find and climb Hill 609, a fortified German mountain fortress during World War II.

Returning to the U. S. he served as editor for the "Florida Outdoors Magazine" wrote free-lance features for sport diving and sport fishing magazines throughout the country, for the last 20 years has contributed articles on these subjects as Editor-At-Large for the "Florida Sportsman Magazine". Over the years Burgess has written and published over twenty books on such subjects as sharks, underwater archaeology, treasure diving, cave diving and Ernest Hemingway. In January 1994, Scuba Schools International awarded Robert Burgess their most prestigious award, given only to divers with verified log books who have met or exceeded all their requirements, including at least 5,000 dives, to achieve the elite SSI rating of Platinum Pro 5000 Diver. Robert F. Burgess lives in north Florida, where he continues to write magazine books; the Mystery of Mound Key - 1966 A Time For Tigers - 1968 Where Condors Fly - 1968 The International Diners Phrase Book - 1965 Sinkings, Salvages And Shipwrecks - 1970 The Sharks - 1970 Exploring A Coral Reef - 1972 Ships Beneath The Sea - 1975 The Cave Divers - 1976 Gold, Galleons And Archaeology: The History Of The 1715 Spanish Plate Fleet And The True Story Of The Great Florida Treasure Find - 1976 They Found Treasure - 1977 The Man Who Rode Sharks - 1978 Man: 12,000 Years Under The Sea, A Story Of Underwater Archaeology - 1980 Secret Languages Of The Sea - 1981 Florida's Golden Galleons: The Search For The 1715 Spanish Treasure Fleet - 1982 Handbook Of Trailer Sailing - 1984 Sunken Treasure: Six Who Found Fortunes - 1988 Diving Off The Beaten Track - 1995 Hemingway's Paris And Pamplona, Then And Now - 2001 Moving To Majorca - 2001 Snorkelers' And Divers' Guide To Old Shipwrecks Of Florida's Southeast Coast Information about Robert F. Burgess, as well as a listing of his available works.

The Photographic Art of Robert F. Burgess with information on how the photographs were made. For more books by Robert F. Burgess